1. Field of the Invention
This invention relates to casting and molding equipment and, particularly, to automatic equipment for die casting and injection molding.
2. Prior Art
Die casting and injection molding equipment is well known in prior art. This type of equipment is characterized by some form of metal mold, usually a simple two-piece mold with a stationary platen, a movable platen and an ejector plate. A means (pot) is provided for retaining molten metal or a heating chamber for plastic pellets of some form, with an injection means for injection of a pre-determined amount of metal or plastic into the mold under relatively high pressures so as to very quickly completely fill the mold before the material solidifies. After molding (e.g. injection) the mold will be left closed for a moment and, in some instances, a coolant circulated through the mold for cooling purposes. The movable platen is then withdrawn and the molded parts are removed therefrom.
In die casting equipment molten metal of the appropriate temperature is maintained in a pot and a piston-cylinder arrangement, typically hydraulically driven, is used for injection. In injection molding machines other types of injectors are also known, such as, by way of example, leadscrew injectors. In any event, while certain details of the equipment vary from manufacturer to manufacturer and from die casting equipment to injection molding epuipment, these differences in design are well known and are relevant to the present invention only in that the present invention is not limited to the specific apparatus disclosed herein, but is readily usable in other types of die casting equipment and in injection molding equipment. Thus, in the remainder of this Prior Art Section and for purposes of explanation of a preferred embodiment, the present invention will be described with respect to a specific die casting machine, it being understood that this is for purposes of explanation only, and the invention is not to be so limited thereby.
The operating cycle of a typical die casting machine is first, the closing of the mold; second, the injection of the molten metal; third, the cooling and solidifying of the molten metal while the mold remains closed; fourth, the opening of the mold, typically with the molded parts and the spider designed to hang up on the moving part; and, five, the removal of the spider and molded parts as one piece, perhaps after the moving portion has engaged injection pins to eject the casting from the movable mold half. This cycle has been utilized for a great number of years with very little change, though individual details of the equipment, of course, have been improved over that time.
Once the casting is removed from the die casting machine, the individual parts had to be removed from the spider and any flash that occurred also removed from the parts. For some parts this might be accomplished by hand, though for repeatability of results, and particularly for larger parts, some form of punch and die is used to accurately separate all the finished parts from the spider whereupon the spider is returned to a breakdown pot to be remelted. Often the casting as removed from the die casting is dipped in water to aid in the cooling thereof and to facilitate handling and die trimming.
There are a number of problems and disadvantages with the prior art die casting machines, which are now becoming fairly severe. Typically, an operator wearing an asbestos glove reached between the mold halves to receive the casting and remove it therefrom for cooling and later placement in the punch press. Obviously, this operation required an operator and also required not only a punch and die, but a complete punch press-type of machine to operate the die trimming. At the present time safety standards are being imposed which prevent an operator from reaching between the mold halves in a die casting machine, or, for that matter, between the punch and die of the punch press. Thus, if the operation is to be done manually as before, long tongs must be used to handle the casting, (e.g. to reach between the mold halves and the punch and die) thereby making handling difficult and tending to slow down the operation.
As an intermediate solution to the problem, equipment is commercially available for mounting on or adjacent to the die casting machine and referencing with respect thereto so as to automatically reach between the mold halves when the mold is open to remove the casting and to transport the casting to the cooling stage or through a cooling stage or through a cooling stage to a punch press. In essence, this equipment merely performs the function of a mechanical man, thereby replacing the operator with the tongs to meet the safety requirements and to provide a more automated operation. This solution, however, has its limitations in that in addition to the die casting machine and the punch press, the mechanical man is also required, the cost of which may be greater than the cost of the punch press and substantial even in comparison to the cost of the die casting machine. It is a complicated machine having its own maintenance and reliability problems. It is a machine which must be set up for each specific casting and in relation to the physical location of the die casting machine and punch press. Even then when all three machines are operating as desired the spiders must be accumulated at the punch press and manually returned to the pot to be remelted and transported back to the die casting machine.
In U.S. Pat. No. 3,328,853 entitled Die Casting and Trimming Machine, there is disclosed a machine in which a gate is coupled to a turntable rotatable about one tie bar of the machine so as to rotate the casting outward from the platens to a separate punch press machanism for trimming the castings. In U.S. Pat. No. 3,547,181 a multiaxis turntable is provided between the platens for performing additional operations between the platens. This apparatus uses a transverse slide mechanism for stripping the spider from the turntable and uses a separate turntable drive independent of the platen drive to provide the desired turntable motion.
Thus, there is a need for automatic die casting equipment and automatic injection molding equipment which will automatically cast or mold parts, shear or punch the parts from the spider for delivery at a desired location and perform such further operations as pre-determined cooling of the casting and eventual return of the spider to the pot of the die casting machine through the use of simplified structure and a minimum of independent drive mechanisms.